Radiation fills the Universe

Content on this page requires a newer version of Adobe Flash Player.

This is
where the Big Bang officially begins. Somehow at the end of the inflationary
era, the Universe was left in a small, hot, dense quantum state. The so-called
vacuum energy of the quantum fields changes into a seething
soup of photons, gluons and other elementary particles. In the Einstein equations
of general relativity, the expansion of the Universe can be driven by energy
density in the form of matter and radiation. During the first phase of the Big
bang, the radiation part of the energy density is so much bigger than the matter
part of the energy density that we can forget matter exists, at least for a
while.